car·ci·no·em·bry·on·ic antigen 
(kär′sə-nō-ĕm′brē-ŏnĭk)
(kär′sə-nō-ĕm′brē-ŏnĭk)n. Abbr. CEA
A glycoprotein present in fetal gastrointestinal tissue and in the cells or serum of adults having certain cancers. It is used clinically to monitor the effectiveness of a treatment, as for colorectal cancer.